Dependence of impact regime boundaries on the initial temperatures of projectiles and targets

Towards higher impact velocities,ballistic events are increasingly determined by the material temperatures.Related effects might range from moderate thermal softening to full phase transition.In particular,it is of great interest to quantify the conditions for incipient or full melting of metals during impact interactions,which result in a transition from still strength-affected to hydrodynamic material behavior.In this work,we investigate to which extent the respective melting thresholds are also dependent on the initial,and generally elevated,temperatures of projectiles and targets before impact.This is studied through the application of a model developed recently by the authors to characterize the transition regime between high-velocity and hypervelocity impact,for which the melting thresholds of materials were used as the defining quantities.The obtained results are expected to be of general interest for ballistic application cases where projectiles or targets are preheated.Such conditions might result,for example,from aerodynamic forces acting onto a projectile during atmospheric flight,explosive shapedcharge-jet formation or armor exposure to environmental conditions.The performed analyses also broaden the scientific understanding of the relevance of temperature in penetration events,generally known since the 1960s,but often not considered thoroughly in impact studies.

Impact of summer office set air-conditioning temperature on energy consumption and thermal comfort

To explore the relationship between summer office set air-conditioning temperature and energy consumption related to air conditioning use to provide human thermal comfort,a comparison experiment was conducted in three similar offices at temperatures of 24,26 and 28 ℃ respectively. A thermal comfort questionnaire survey was conducted. It is demonstrated that air-conditioner energy consumption at the set temperature of 28 ℃ is 113% and 271% lower than at 26 ℃ and 24 ℃,respectively. A linear relationship exists between air-conditioner energy consumption and the indoor and outdoor temperature difference. When comfortably dressed,over 80% of research participants accept the set temperature of 28 ℃. The regression analysis leads to a neutral temperature of 26.2 ℃ and an acceptable temperature of 28.2 ℃ for over 80% of the research participants subjects,indicating that the current 26 ℃ set temperature for offices in summer,required by Chinese General Office of the State Council,can be increased to 28 ℃. Moreover,analysis of predicted mean vote(PMV) index shows that a set temperature of 27 ℃,not 26 ℃,is sufficiently comfortable for office staff wearing long-sleeve shirts,long pants and leather shoes.

Evaluation of Energy Band Gap, Thermal Conductivity, Phase Transition Temperature and Elastic Response of PS/CdS Semiconducting Optical Nanocomposite

Thick film of Polystyrene (PS)/CdS semiconducting optical nanocomposite has been synthesized by dispersing nanofiller particles of CdS in PS matrix. The nanostructure of the CdS particles has been ascertained through X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). Small angle x-ray scattering analysis has been performed in order to ascertain nanocomposite character of the PS/CdS sample. Scanning Electron Microscopy (SEM) analyses of these samples have been carried out to establish the surface morphology. Optical Absorption Spectroscopy is used to measure the energy band gap of PS/CdS nanocomposite by using Tauc relation whereas Transient Plane Source Technique is used for the determination of thermal conductivity of the prepared samples. The phase transition temperature and elastic response of the prepared samples have been ascertained through Dynamic Mechanical Analyzer (DMA). This study reveals that the thermal conductivity, Young’s modulus and the toughness of the material are greatly influenced by the existence of interfacial energetic interaction between dispersed CdS nanofiller particles and matrix of PS.

Using Parallel Packed Bed within a High Temperature Thermal Energy Storage System for CSP-Plants

In order to optimize the electricity yield of CSP （concentrated solar power） plants, TES （thermal energy storage） systems are regarded as an essential component. Furthermore, for many electricity grid operators, it is important to have spinning reserves in the grid and dispatchable power available, both offered by CSP-plants with integrated thermal energy storage. Enolcon is developing a new TES-system since several years. The system itself was designed to offer a principle simple and robust setup （with regard to execution and operation） and which is reducing the electricity costs of CSP-power plants by the consequent use of state of the art technology. Furthermore, such system shall be open to future developments of CSP-systems with regard to increasing steam temperatures and steam pressure. Such TES-system shall be commercially available for large scale application already in year 2014/2015. The key elements of the enolcon-TES are the open cycle using always ambient air with an air-air-heat exchanger and the arrangement of the storage material in such way to minimize the pressure losses and the own electricity consumption. The development is progressing in a structured way by studies, engineering works, TES-pilot plants, isothermal air flow test plant for the verification of the CFD-calculations, and since end of 2012 by the operation of a high temperature TES-module with all features of the large scale modules.

High temperature polyimide nanocomposites containing twodimensional nanofillers for improved thermal stability and capacitive energy storage performance

Future electronic devices toward high integration and miniaturization demand reliable operation of dielectric materials at high electric fields and elevated temperatures.However,the electrical deterioration caused by Joule heat generation remains a persistent challenge to overcome.Here,the solution-processed polyimide(PI)nanocomposites with unique two-dimensional(2D)alumina nanoplates are reported.Substantial improvements in the breakdown strength,charge–discharge efficiency and discharged energy density at elevated temperatures have been demonstrated in the composites,owing to simultaneously suppressed conduction loss and increased thermal conductivity upon the incorporation of 2D Al_(2)O_(3) nanofillers possessing excellent dielectric insulation and thermophysical properties.The predominance of Al_(2)O_(3) nanoplates in enhancing thermal stability and high-temperature capacitive performance over nanoparticles and nanowires is validated experimentally and is further rationalized via finite element simulations.Notably,the Al_(2)O_(3) nanoplates filled PI nanocomposite exhibits a hightemperature capability up to 200℃ and remarkable efficiency(e.g.≥95% at 200 MV/m)over a wide temperature range,which outperforms commercial dielectric polymers and rivals the state-of-the-art polyimide nanocomposites.

Research progress on protective coatings against molten nitrate salts for thermal energy storage in concentrating solar power plants

Concentrating solar power(CSP) has garnered considerable global attention as a reliable means of generating bulk electricity, effectively addressing the intermittent nature of solar resources.The integration of molten salt technology for thermal energy storage(TES) has further contributed to the growth of CSP plants;however, the corrosive nature of molten salts poses challenges to the durability of container materials, necessitating innovative corrosion mitigation strategies.This review summarizes scientific advancements in high-temperature anticorrosion coatings for molten nitrate salts, highlighting the key challenges and future trends.It also explores various coating types, including metallic, ceramic, and carbon-based coatings, and compares different coating deposition methods.This review emphasizes the need for durable coatings that meet long-term performance requirements and regulatory limitations, with an emphasis on carbon-based coatings and emerging nanomaterials.A combination of multiple coatings is required to achieve desirable anticorrosion properties while addressing material compatibility and cost considerations.The overall goal is to advance the manufacturing, assembly, and performance of CSP systems for increased efficiency, reliability, and durability in various applications.

Proposal of a Solar Thermal Power Plant at Low Temperature Using Solar Thermal Collectors

To this day, only two types of solar power plants have been proposed and built: high temperature thermal solar one and photovoltaic one. It is here proposed a new type of solar thermal plant using glass-top flat surface solar collectors, so working at low temperature (i.e., below 100°C). This power plant is aimed at warm countries, i.e., the ones mainly located between -40° and 40° latitude, having available space along their coast. This land based plant, to install on the seashore, is technologically similar to the one used for OTEC (Ocean Thermal Energy Conversion). This plant, apart from supplying electricity with a much better thermodynamic efficiency than OTEC plants, has the main advantage of providing desalinated water for drinking and irrigation. This plant is designed to generate electricity (and desalinated water) night and day and all year round, by means of hot water storage, with just a variation of the power delivered depending on the season.

Determination of Comfort Conditions Using the PMV, Set and PDD Thermal Comfort Indexes in Ivory Coast

This work falls within the context of reducing energy consumption in Côte d’Ivoire. As the building sector is one of the energy consumers worldwide, it could be a major source of energy savings. A major source of energy savings. With this in mind thermal comfort in buildings in Côte d’Ivoire (Abidjan) in order to determine (Abidjan) to determine thermal comfort conditions. To carry out study, measurement campaigns were carried out in various buildings. These measured parameters were used to calculate comfort indices such as PMV, PDD, SET and operating temperature. A correlation was then made between the PMV index and the operating temperature, then between the SET and the operating temperature to determine the thermoneutrality temperature and the different thermal comfort thermal comfort ranges. The PMV gave a thermoneutrality temperature of 24.87˚C in the rainy season and a thermoneutrality temperature of 25.15˚C during the dry season. In addition, the SET gave comfort ranges, with values ranging from 23.23˚C to 25.70˚C in the rainy season and 23.35˚C to 26.08˚C in the dry season. In addition, the acceptability predicted by the PDD showed that in the rainy season, the premises were more acceptable than in the dry season.

Assessing the energy saving potential of using adaptive setpoint temperatures:The case study of a regional adaptive comfort model for Brazil in both the present and the future

It has been found in recent years that using setpoint temperatures based on adaptive thermal comfort models is a successful method of energy conservation.Recent studies using adaptive setpoint temperatures incorporate international models from ASHRAE Standard 55 and EN16798-1.This study,however,has instead considered a regional Brazilian adaptive comfort model.This study investigates the energy demand arising from the use of a local Brazilian comfort model in order to assess the energy implications from the use of the worldwide ASHRAE Standard 55 adaptive model and various fixed setpoint temperatures.All of Brazil’s climate zones,full air-conditioning,mixed-mode building operating modes,present-day climate change scenarios,and future scenarios—specifically Representative Concentration Pathways(RCP)2.6,4.5,and 8.5 for the years 2050 and 2100—have all been taken into account in building energy simulations.The use of adaptive setpoint temperatures based on the Brazilian local model considering mixed-mode has been found to significantly reduce energy consumption when compared to static setpoint temperatures(average energy-saving values ranging from 52%to 58%)and the ASHRAE 55 adaptive model(average values ranging from 15%to 21%).Considering climate change and the mixed-mode Brazilian model,the overall energy demand for the three groups of climatic zones(annual average outdoor temperatures≤21℃,>21 and≤25℃and>25℃)ranged between 2%decrease and 5%increase,4%and 27%increase,and 13%and 45%increase,respectively.It is concluded as a consequence that setting setpoint temperatures based on the Brazilian local adaptive comfort model is a very efficient energy-saving method.

Integrated utilization of low-grade thermal energy in hot coal mine

This paper explores the integrated utilization of low-grade thermal energy in hot coal mines, based on analysis of original heating, refrigerating, mine draining, bath draining and air exhaust systems, and in combination with the actual conditions of Tangkou Coal Mine in Shandong Province. It presents a set of comprehensive and integrated utilization schemes for the various different kinds of low quality heat energy. With heat pumps, the recycling of the low quality heat energy from the drainage, bathing water and the exhaust air can occur in winter, and in summer, there exists condensed heat of the refrigerating system. When in conjunction with solar collectors, the thermal utilization of solar power can be realized for the whole year. The system achieves mine drainage and bathing water purification and recycling, as well as purifying exhaust air by water spraying. It also satisfies the demands of a whole year＇s bathing heat for the coal mine, with refrigeration in summer, and heating for the ground house and shaft house in winter. It is able to integrate different kinds of low quality heat energy and low emission drainage and dust, and can replace the traditional boiler heating system. Finally, the system reduces conventional energy consumption and the amount of mine water drainage.

Electromagnetic and Thermal Characteristics of Molybdenite Concentrate in Microwave Field

In modern metallurgical industry,microwave thermal technique has many advantages as one efficient energy treatment in an electromagnetic form,such as internal self-generated heat,easy access to control a volumetric heating process,and consensus on cleanliness,convenience and high efficiency of energy use.Both permittivity and permeability of molybdenite concentrate were measured for a further discussion about its electromagnetic heating coupling.A bidirectional coupling physics field in numerical modeling was undertaken to evaluate the microwave absorption potential and dielectric heating performance of molybdenite concentrate by the multi-physics finite element method.The electromagnetic morphology and the field distribution strength were described in the microwave reaction cavity.The electromagnetic field strength and the dissipation coefficient induced by temperature variation were represented throughout the whole heat chamber and at key parts of interest.Dependent temperature distribution was compared with that being obtained from a scenario by thermal conduction with a stable heat source.The molybdenite concentrate would be heated at surrounding temperature up to 593℃for 10 min by microwave energy that was transmitted by a rectangular waveguide.Scanning electron microscopy(SEM)patterns suggested that the polished and neat crystalline molybdenum trioxide(MoO_(3))products were achieved by the microwave heating process.The superiority via utilizing microwave thermal technique is expounded in the preparation strategy for molybdenum oxide or molybdenum metal.

Analysis of indoor set-point temperature of split-type ACs on thermal comfort and energy savings for office buildings in hot-humid climates

In hot-humid climates,particularly in sub-Saharan Africa(SSA),ambient temperatures and relative humidity are as high as 35°C and 84%,respectively,requiring the use of mechanical cooling systems for indoor thermal comfort.Split-type vapor-compression air-conditioners(SVAC)are mainly used for space cooling in SSA and consume 60-80%of total energy consumption in commercial and public buildings.Appropriate control strategy of the indoor set-point temperature of SVAC can result in significant energy savings in these buildings.In this study,modeling and dynamic simulation have been conducted using EnergyPlus to predict the energy saving potential and indoor thermal comfort of buildings in hot-humid climates by controlling set-point temperature of the SVAC.In a case study,climatic data for Ghana,was used to predict the energy saving potential and indoor thermal comfort.The study results revealed that,to ensure indoor thermal comfort at high outdoor temperature condition of 35°C,the least and optimum set-point temperatures of the SVAC should be 21°C and 25°C,respectively.On the other hand,for low outdoor temperature condition,the least and optimum set-point temperatures were 22°C and 26°C,respectively.Considering 1-star and 2-star rated SVACs which are dominantly used in Ghana,operating at 21-25°C in the case of high outdoor conditions,and 22-26°C for low outdoor conditions relative to the least temperatures resulted in energy savings of 8-33%and 12-44%,respectively.

Thermocline Thickness Evaluation on Stratified Thermal Energy Storage Tank of Co-generated District Cooling Plant

Temperature distribution of water inside of thermal storage tank reflects the condition of cooling energy stored in the tank. It can be used to define important parameters required for evaluation the performance of thermal storage tank. In this study, the thermocline thickness was evaluated for two cases of charging cycles： case Ⅰ at 393 m^3 / hr and case Ⅰ at 524 m^3 / hr. Hourly data were used for the study. Curve fitting approach was used to plot the temperature distribution profiles. Results obtained revealed that the fitting function enabled quantification of thermocline thickness of the thermal storage tank. The parameters that were determined are average cool-warm water temperatures and cool water depth in the tank. The approach offer an advantage to determine the thermocline thickness based on functionally relationship of temperature distribution profile. Results obtained shown that thermocline thickness increases at the higher flow rate. This was due to increased mixing of cool and warm water. It was also noted that thicker thermocline occurred in the region nearby the inlet diffuser. The findings indicate that the operating thermal energy storage as performing as a stratified tank.

Anomalous low-temperature heat capacity in antiperovskite compounds

The low-temperature heat capacities are studied for antiperovskite compounds AX M_3（A = Al, Ga, Cu, Ag, Sn, X = C,N, M = Mn, Fe, Co）. A large peak in（C- γ T）/T^3 versus T is observed for each of a total of 18 compounds investigated,indicating an existence of low-energy phonon mode unexpected by Debye T^3 law. Such a peak is insensitive to the external magnetic field up to 80 k Oe（1 Oe = 79.5775 A·m-1）. For compounds with smaller lattice constant, the peak shifts towards higher temperatures with a reduction of peak height. This abnormal peak in（C- γ T）/T^3 versus T of antiperovskite compound may result from the strongly dispersive acoustic branch due to the heavier A atoms and the optical-like mode from the dynamic rotation of X M_6 octahedron. Such a low-energy phonon mode may not contribute negatively to the normal thermal expansion in AX M_3 compounds, while it is usually concomitant with negative thermal expansion in open-structure material（e.g., ZrW_2O_8, Sc F_3）.

深层地热能丛式多分支U型井采热技术及传热算法

深层地热能是一种分布广、资源量大具有发展前景的可再生新能源,当前的主要开采方法有增强型地热系统(EGS)、环绕式井筒换热系统(AGS)、断层带流体循环开采和同轴套管开采法,但存在采热功率不稳定、地震风险高和采热效率低等难题。针对当前深层地热开采技术面临的瓶颈问题,本文以开采过程只有能量交换而没有物质交换为原则,以深层干热岩地热规模化可持续稳定开发为目标,提出了深层地热能丛式多分支U型井采热方法(UMW-DGS)及关键技术,在此基础上建立了井筒轴对称热传导模型,以青海共和盆地恰卜恰深部干热岩储层为背景,提出了高温高压岩石热导率测试新方法,计算了在定井径条件下井周温度场和采热功率的时空演化规律,分析了温度差、热导率和井径等3个敏感因素对采热功率的影响。此外,针对UMW-DGS定解问题,研发了基于有限体积法(FVM)的三维热流固耦合数值算法,研究了UMW-DGS单水平井段换热效率和在不同泵注量条件下温度场时空演化。通过分析不同流量的有效换热量、换热时长和功率发现:泵注流量的增加会导致有效换热能量和有效换热时长的降低,并且使有效换热功率先增加后减少。研究结果表明,深层地热能开发需要在平衡换热温度和功率的条件下设计注入排量,从而得到最优的换热效果。

有机基相变材料的研究与应用

相变材料(PCM)是一种可逆的储能材料,在实际使用中可以周期性的以相变潜热的形式储存能量以达到节能的效果。针对相变温度为中低温的有机基相变材料(OPCM)进行了探讨,其具有长期的化学稳定性,无污染且节能、高效、无毒无腐蚀性。归纳综述了国内外有机基相变材料的制备以及OPCM包封技术的最新研究成果,根据材料的特点介绍了降低可燃性的方法以及在各个领域的最新应用。

双层地基中高导热能量桩热力学特性研究

通过室内模型试验,针对不同循环次数与桩顶荷载作用下高导热能量桩热力学特性进行研究。结果表明:桩身与土体温度随着循环次数增加存在累积行为,距离桩中轴线越远,土体温度越低,变化越小;桩身附加温度应力沿深度方向先减小后增大,最大附加温度应力位于-257 mm处,附加温度应力随着桩顶荷载和循环次数增加而增大;随着桩顶荷载增大,循环后桩顶沉降增大,桩顶沉降随着循环次数增加存在累积行为,在能量桩设计时予以充分考虑。

Experimental study on thermal characteristics of a double skin faade building

An experimental study of the thermal characteristics of an existing office building with double skin facade DSF were conducted in hot summer daytime in Nanjing China. The temperature distributions of the DSF and indoor environment were measured at different control modes of DSF.The results show that the energy consumption of the air conditioning system in room B with opened exterior vents a closed interior facade and an air cavity with shading was 21.0% less than that in room A with closed exterior vents a closed interior facade and air cavity without shading in 9.5 h. The temperature distributions of the DSF and indoor environment in both horizontal and vertical directions were decisively influenced by shading conditions. The usage of shading devices strengthens the stack effect on the air cavity. Compared to room A the temperature distribution in room B is more uniform with smaller fluctuations.Meanwhile the problem of overheating in the air cavity of the DSF is still present in all tested conditions.

履带车辆油气弹簧生热机理和热模型研究

为研究油气弹簧工作过程中的生热机理,建立油气弹簧参数化热模型。采集试验数据对油气弹簧阻尼示功特性进行数值拟合,得到活塞运动速度-阻尼力关系的数学表达式。对油气弹簧的传热路径和换热特点分析,建立油气弹簧热阻网络模型,计算得到工作过程中油气弹簧2种工作介质的温度变化特性。设计试验对油气弹簧的热模型计算结果进行验证。试验结果表明:阻尼力做功是油气弹簧温度升高的主要热量来源,油液温度比气体温度上升更快、平衡温度更高,该模型可以准确地计算出油气弹簧不同工作介质的温升情况,为油气弹簧热-机耦合动力学研究提供了参考。

激光照射岩石热裂特性与裂隙分布研究

激光辅助破岩是一种非接触式破岩技术,破岩效果主要受激光功率、照射时间和离焦距离等参数影响。选择石灰岩、砂岩和花岗岩3类岩石,开展了不同照射参数的破岩试验,分析了温度、射孔参数、比能、热裂效能、裂隙分布、矿物组分和微观结构等变化规律。结果表明,激光照射下3类岩石表面温度均超过2000℃、温度梯度最高可达1500℃/mm,相同位置处花岗岩表面温度和温度梯度最高、砂岩次之、石灰岩最低;3类岩石射孔直径、射孔深度和射孔速率均与照射参数密切相关,砂岩、石灰岩和花岗岩最大射孔速率分别为3.18,2.68,0.8 mm/s。相同照射参数下,比能较热裂效能高1~2个数量级,3类岩石比能排序为:花岗岩>石灰岩>砂岩。照射后岩样均存在数条主裂隙,沿径向延伸至试样边缘,石灰岩和花岗岩次生裂隙发育,砂岩未发现明显次生裂隙。照射后岩石矿物衍射强度和微观结构发生显著改变。